1. Field of the Invention
The invention relates to a yarn brake comprising a movable sheet or plate-like lamellar brake shoe which can be urged by an actuating device against a fixed brake shoe in order to brake a yarn running between the brake shoes.
2. Description of the Related Art
Yarn brakes of the above type are described in the French patent documents A 1 161 662 and 2 300 734 and Italian patent document 593 034. As regards these designs, the movable brake shoe is pressed by its own weight, or by a magnetically adjustable force and/or by a pneumatically adjustable force against a fixed brake shoe. Such yarn brakes incur the drawback that they may damage the yarns, and/or rupture them, in particular when these yarns include nubs or thicknesses and/or other irregularities.
A yarn brake is known from the German patent document 21 30 670 which is fitted with two pairs of movable, lamellar brake shoes. Each brake shoe is mounted in a jam-free manner on two pins for which it is fitted with appropriately large clearances. An electromagnet is mounted between the two pairs of brake shoes, and the armature of the electromagnet is fitted with a bridge resting against the outer brake shoes and which it presses against the inner ones.
Moreover, a yarn tensioner or yarn brake is known from the British patent A 20 93 488, such brake comprising two lamellar brake shoes enclosing the yarn to be braked. This yarn brake includes an electromagnet constituting two pole pieces. A first lamellar brake shoe made of a non-magnetic material rests against the two poles pieces. The second and outer brake shoe is made of a magnetizable material and can be pulled magnetically against the non-magnetizing brake shoe. The two lamellar brake shoes are substantially vertical and fitted onto two pins. The path of the yarn to be braked is horizontal and located substantially along the center of the two brake shoes.
The Swiss patent document A 68 21 48 discloses a yarn brake arranged to brake two yarns running parallel to each other each at two consecutive positions. The brake comprises three lamellar brake shoes, that is, one central brake shoe and two outer ones. The yarns run on each side of the central brake shoe and as a result can be braked in each case between the central and one outer brake shoe. The three brake shoes are held by an edge running parallel to the path of the yarn in a hook-shaped guide. One of the two outer brake shoes always rests against one wall of a support. The opposite outer brake shoe is adjustably spring-loaded and can be pressed against the central and the other outer brake shoe. The yarn path is between the brake shoe edges guided in a hook guide and a position where the loading force is applied.